Dye



Patented Jan. 25, 1944 DYE Herbert B. Charmbury, State College, Pa.,asslgnor to Pennsylvania Bituminous Coal Research, Inc., Altoona, Pa..'a corporation of Pennsylvania No Drawing. Application March 25, 1941,Serial N0. 385,150

11 Claims. (Cl. 260-644) This invention relates to dyes and woodstains.

The major object of the invention is to provide dyes that are madedirectly from coal, and more particularly dyes capable of the directdyeing not only of wool, silk, wood and other natural fibers oflignocellulose, protein-like or carbohydrate nature, but also ofsynthetic fibers, with production of dyed products which are fast undervarious conditions to which the dyed products may be exposed.

A further object is to provide a method of making dyes of the foregoingcharacter directly from coal, which is cheap, easily practiced,efiicient, readily controlled, and requires no complicated, expensive ordiflicultly operable apparatus.

- The invention is predicated upon my discovery that dyes may be madedirectly from coal by subjecting the coal to treatment with nitric acidat a temperature above room temperature to effect conversion of reactivecarbonaceous constituents of the coal into reaction products capable ofdyeing various kinds of fibers. Such reaction products may then beextracted from the treated coal and after separation from immiscibletarry and oily matter, if present, they are adapted for direct use fordyeing or staining purposes.

In the practice of the invention conversion of carbonaceous constituentsof coal into brown dyes may be accomplished by treatment of the coalwith nitric acid. Any of the coals up to, but not including, anthracitesmay be used for the purposes of the invention, i. e., the dyestufis madein accordance with the invention may be produced from lignites,bituminous coals, and subor semibituminous coals. Such treatment may be,effected with the acid in either the liquid or the vapor phase. Frommany standpoints, however, liquid phase treatment is simpler and morereadily controlled, for which reason the invention may be exemplifiedwith detailed reference thereto.

In the practice of the preferred embodiment of the invention nitric acidand the coalare mixed at room temperature, most suitably by adding theacid to the coal. Thereupon an exothermic reaction sets in which is ofsuch nature that artificial heating of the reaction body isunnecessary.When that reaction has died down the mixture of coal and acid is heatedto complete reaction between the nitric acid and the reactivecarbonaceous constituents of the coal. Such heating is necessarybecause, as I have discovered, without it the dyes are not produced.

The temperature attained during the treatment of the coal should notexceed the decomposition temperature of nitric acid under the conditionsunder which the treatment is effected, for which reason it is desirableto add the acid incrementally to the coal. It is desirable also tooperate under a refluxcondenserto minimize acid losses. For mostpurposes I have found that the reaction is completed smoothly,satisfactorily and relatively expeditiously at atmospheric pressure byheating the reaction body on a water or steam bath, wherebydecomposition of the acid does not occur, at least to any excessive orobjectionable extent. If desired, the reaction might be carried out atpressures above or below atmospheric.

The proportions of acid and coal used may be varied considerably,although for economic reasons they will depend in part upon theconditions of operation. Thus, in the case of treatmentof coal withsolutions of nitric acid in a container provided with a reflux condenserI have found that as the ratio of acid (sp.gr. 1.4) to coalis increasedfrom, for example, one part by weight of each, the amount of dyeproduced is increased progressively until at a ratio of from'4 to 8Ipartsof acid to 1 part of coal the yield of the desired dyestuff isapparently at a maximum so that for ordinary purposes under suchconditions of operation greaterproportions of acid are of no advantage.In this range where optimum yield is obtained the lower ratios-of acidto coal, say-in the vicinity of 4 to 1 may be used by prolonging theheating as compared with the case where the higher ratios e. g., about 8to 1, are used. Where, however, the reaction is carried on in containersfreely open to the atmosphere, higher ratios of acid to coal may benecessary to obtain optimum recovery of dye. On-the other hand, in vaporphase operation using nitric acidand air the optimum ratio seems to beabout two parts by weight of acidto'one part byweight of coal;

Apparently there'is nothing critical in the particle size of thecoal'being treated. Tests have shown, for example, that essentially thesame results are obtained with coal of one-half inch size as with coalground to pass a ZO-mesh sieve. 7

After the reaction between the coal-and the nitric acid-hasbeencompleted the excessacid is removed and the treated coal is then washedwith water to remove residual acid, as by washingwith repeated changesof water.- The acidic liquors may be distilled to recover the acid, andupon evaporatin to dryness a solid product of unknown composition isrecovered. The washed and treated coal is then ready for extraction .ofthe dyest-uif. I have found that two dyestuffs may be Thus, byextraction with certain neutral or, and preferably, acidic solventsthere is recovered a brown dyestuff, and if the thus-treated coal bethen extracted with alkali there is recovered another brown dyestufi.Or, if thecoal treated as described above be extracted first withalkali, all of the dyestuff of both types is recovered directly, and formany purposes such extraction is preferred.

Referring first to direct alkaline extraction, there may be. used anaqueous solution of an alkali, for instance sodium hydroxide orpotassium hydroxide. Ammonium hydroxideis,ihowever unsatisfactory,unless it is very .dilute, ,e. g. about 0.1 normal. Very dilutesolutions of other alkalies sufice, and they are preferred for reasonswhich will appear hereinafter. The extraction may be carried out at roomtemperature although it is hastened by moderate heating, preferably notbeyond about 100 C. The most satisfactory results appear to be had byextraction below about 50 0. Complete extraction of dy from the treatedcoal will depend upon the volume of solution and the alkaliconcentration, but multiple extractions with fresh lots of'the alkalisolution are desirable, the separate extracts being combined, ifdesired, for "further treatment.

The alkaline extracts are of brown color, the exact shade depending uponthe concentration of dye taken up from the coal. "If th alkali solutionusedfor extraction is-sufficiently dilute, say "0.1 normal, the extractsmay be used for dyeing. But if concentrated alkalies are used theextracts are useless as dyeing agents 'because they con'tainimmiscibletarry and oily matter which prevents the attainment o'fsa'tisfactorydyeing, and particularly is this the case as the extraction temperaureis raised above room temperature. I have discovered, however, that ifsuch solutions be freed "from the immiscible tarry and oily matter,they, or solutions of the solid dyestuif recovered therefrom, may then"be used directly for satisfactory dyeing of wool, silk, suchartificially produced fibers as :those sold under the trade-mark Nylon,and other fibers of generally similar nature. To this end the tarry andoily matter, when present, may beremoved from the alkaline solution invarious ways, as by filtering the solution or by the use of selectivesolvents which will remove the tars and oils butin which the dye isinsoluble. Satisfactory separation can be effected also in simple andinexpensive fashion by steam distillation.

The solutions, freed from tarry and oily matter when present, maybe usedfor direct dyeing. Where it is desirable to have the material in solidform, however, the solutions maybe evaporated to dryness thus producingasoluble .solid which may be redissolved in water to produce dyeingsolutions, but when this is done the dye bath should contain sodiumsulfate or other equivalent salt the use of which .is understood in thedyeing indutsry. As intimated above, the exact color produced willdepend upon the concentration of the solution, whether it be theoriginal or dilute solution of alkaline extract or a solution made fromthe dried productobtained by evaporation thereof.

In addition to the reason -pointed :out above, thexuse of very dilutesolutions .of alkali and-of relatively low extraction temperatures aredesirable also because the possibility of damaging the fabric by alkaliis minimized. However, where the separation from tarry matterl-ls notiorganic acidic agents.

objectionable, concentrated alkaline extracts may be diluted to avoiddamage to the fabric.

As pointed out above, one type of dyestuif may be removed from thetreated coal by extracting it first with certain neutral or acidicsolvents, and this material appears to be different from that obtainedby extracting the treated coal with alkali solutions, although both arebrown dyes.

.Neutral extracting solvents may be used for this purpose, butpreferably there are used Aqueous solutions of inorganic .acids, such ashydrochloric acid, appear to offer little or no advantage over water,which might be used, astaneutral solvent, but which is not advantageousbecause the solubility of the dye in it is low and large volumes areneeded. Aqueoussolutions of organic acids such as acetic, benzoic andphthalic acids have a considerable solvent effect on the dye, whilecertain organic acids such as glacial acetic acid appear to give thebest results. Other organic acidic materials that may be used arephenol, resorcinol and the like.

Various methods of carrying out the extraction are applicable. It hasbeen found that the use of a standard type of extraction apparatus, suchas the 'Soxhlet, gives satisfactory results. The extraction may also beeffected simply by agitatinga mixture of treated coal and solvent. Inthis case it is usually desirable to heat the mixture to theboilingtemperature of the solvent,

since the solubility of the dye increases with increasing temperature.

In a typical test, 25 grains of treated, washed and dried coalwas-extracted in a Soxhlet apparatus with .300 cc. of glacial aceticacid during a-period of approximately 72 hours when extraction'wascomplete. The extracted material was freed from acetic acid byevaporation over a steam bath. The dye thus obtained weighed'4.5;:grams.

The dye Droduced'in this "manner is, after removal of the solvent, adark brown solid which is somewhat soluble in water. Aqueous solutionsof this dye are, .as "in the case of the dyes alkali extracted asdescribed'above, capable of dyeing silk, wool and other fibers brown,the exact shade depending on the concentration. This acid-soluble dyegives lighter shades for the same concentrations than the alkali-solubledyes described hereinabove, and when celanese and ny lonare dyed with itthe dyed fabrics exhibit a fluorescent effect.

The extract after being filtered is optically void in sufiicientlydilute solution, thus showing that "the'dye is in'true solution.Although the exact nature of the reaction by which thereactiveconstituents of coal are converted to dyes is not known, thabsorption spectra of solutions produced in accordance with theinvention indicates the presence of a carbon-nitrogen linkage in thedye, and analysis by appropriate methods has shown that the dye materialcontainshydroxy and carboxyl groups. The nitrogen content of the treatedcoal is substantially greater than that of the original coal. Also, the

conditions: as the composition of the coal treated,

the concentration :of nitric acid or other nitrating and oxidizingagent, the temperature and time of reaction, and the like. Under theconditions outlined above, however, it is ordinarily possible todissolve about 70 to 90 per cent by weight of the coal treated. If theinert constituents of coal, chiefly fusain, mineral matter and water bedisregarded it appears that substantially 100 per cent of the coal isconverted into the soluble matter.

As an example of actual practice, there was used an upper Freeport coalwhose proximate analysis was 7.28 per cent of ash, 31.67 per cent ofvolatile matter, 1.38 per cent of sulfur, and 0.67 per cent of water,and whose ultimate analysis was 80.59 per cent of carbon, 5.17 per centof hydrogen, 1.38 per cent of sulfur, 1.35 per cent of nitrogen, and thebalance essentially oxygen. This coal contained about 3.5 to 4 per centof fusain. 100 grams of the coal, ground to pass a 20-mesh sieve, wasplaced in a 3 litre flask provided with a reflux condenser. A total of800 grams of ordinary concentrated nitric acid (sp. gr. 1.4) was addedin small amounts at a time, the rate of addition being such as to keepthe temperature of the mass below the decomposition temperature of theacid without resort to artificial cooling. After about 400 grams of theacid had been added the reaction subsided to a point such that the flaskwith its condenser attached was placed on a steam bath on which it washeated thereafter, and the balance of the acid was added gradually.About three hours was consumed in addition of the acid. The flask andits contents were then heated for one hour longer, after which heatingwas discontinued. One hour later the contents of the flask were filteredthrough a fiber glass mat, and the coal retained on the mat was thenwashed with distilled water until the runnings were neutral to litmus.The washed and treated coal was then air dried, after analysis showed109 grams of mositure-free coal. As thus dried the coal was ready forextraction. Ten grams of the dried material were placed with 100 cc. of1 per cent sodium hydroxide solution in a glass container and shaken atroom temperature for about 15 minutes. The material was then centrifugedand the supernatent liquid was separated from the deposited solid. Byrepeating such extraction twice substantially all of the dyestuff wasremoved.

The foregoing example illustrates the use of a ratio of 8 parts of acidto 1 of coal. The ability to use lower ratios by extending the heatingtime appears from the following example. Twentyfive grams of the samecoal, ground to pass a 20-mesh sieve, were placed in a 1-liter flaskprovided with a reflux condenser. To the coal there was added cc. of C.P. concentrated nitric acid (sp. gr. 1.4) every five minutes until atotal of 72 cc. of acid had been added. This represents an acid to coalratio of 4:1, in other words, a total of 100.8 grams of acid. After 60cc. of the acid had been added to the coal, the flask was subjected tothe heat of a steam bath, and heating of the acid-coal mixture wascontinued for 3 hours. After the heating had been discontinued forminutes the solution was filtered using a fiber glass mat as a filterbed. The treated coal was then washed with distilled water until theresidual acid was removed; this required about 1 liter of distilledwater. The washed and treated coal was then dried overnight in an ovenat 105 C., and after cooling it was found to weigh 28.3 grams. Threegrams of this treated, washed and dried coal were then added to cc. of0.1N NaOI-I in small portions at a time and with constant stirring. TheNaOH solution became dark brown in color. After the addition of the coalto the solution was completed and stirring had continued for about 5minutes, the solution was poured into a centrifuging bottle. To thebeaker that still contained some undissolved residue was added 100 cc.of distilled water and after stirring this was poured into the samecentrifuging bottle with the above solution. 1 The bottle containing thetotal solution was then placed in the shaker for 5 minutes and finallycentrifuged for 10 minutes. After this the solution was separated fromthe undissolved treated coal by filtration, divided into two parts andused directly as a dye for silk and wool. This yielded a light browncolor on the fibers. The undissolved coal was washed until the washingswere colorless, dried for several hours in an ovenat 0., cooled in adesiccator and found to Weight 0.7 gram.

Dyes made as described hereinabove produce pleasing shades of browndepending, as stated, upon the concentration of the solution, and alsoupon the time and temperature of the bath and the material being dyed.By actual test I have found that the dyed products possess satisfactoryresistance to various deteriorating influences. Thus, tested by standardprocedures wool and silk fabrics dyed with dyes made according to theinvention are fast to water, and washing, at least at temperatures up toabout 100 C., to crocking, and to perspiration. Also, they areapparently resistant to wide variations of acidity and alkalinity, beingresistant to water varying in pH from 4 to 10. The color is, however,bleached by chlorine and other bleaching agents.

Various modifications are permissible, of course. Thus, although theinvention has been described with reference to the use of nitric acid,it will be understood that any agent or combination of agents productiveof nitration and oxidation may be used.

The term bituminous coals as used in the claims includes subandsemi-bituminous coals. as indicated above.

According to the provisions of the patent statutes, I have explained theprinciple and method of practicing my invention and have described whatI now consider to represent its best embodiments. However, I desire tohave it understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically described.

I claim:

1. That method of making a dye from bituminous coals which comprisestreating the coal with nitric acid at a temperature above roomtemperature but below the decomposition temperature of said acid, andthen extracting the treated coal to recover brown dyestufi.

2. That method of making a dye from bituminous coals which comprisestreating the coal with nitric acid at a temperature above roomtemperature but below the decomposition temperature of said acid,washing the treated coal to remove residual acid, and then extractingthe treated coal with a solvent for brown dyestui'l produced thereby.

3. A method according to claim 2, said acid being used in an amountvarying from about 1 part by weight per part of coal to 8 parts byweight per part of coal.

4. That method of making a dye from bitumie. That method of making a dyefrom bituminous coals which comprises treating the coal with nitric acidsolution at room temperature and thereby causing an exothermic reactionto be initiated, permitting said reaction to proceed at room temperatureand then heating the mixture at a temperature not over about 100 C. tocomplete the action of said acid upon the coal, then washing the treatedcoal to remove residual acid, and then extracting brown dyestufi fromthe washed coal.

'7. A method according to claim 6, said acid being used in an amountfrom about one to about eight parts by weight per one part by weight ofcoal, and being added in small amounts at a time.

8. That method of making a dye from bituminous coals which comprisesmixin the coal with nitric acid solution at room temperature and therebycausing an exothermic reaction to be initiated, permitting said reactionto proceed at froom temperatureand then heating the mixture -at.atemperature not over about 100 C. to complete the action of the acidupon the coal, then washing the treated coal to remove residual acid,and extracting the washed coal with an organic acidicmaterial andthereby recovering a brown dye solution.

9. A method according to claim '7, said material being glacial aceticacid.

10. That method of making a dye from bituminous coals which comprisestreating one part by weight of coal with air and nitric acid in thevapor phase :at a temperature at which said acid reacts with reactiveconstituents of the coal, washing the treated coal to remove residualacid, and extracting the Washed coal to recover solution of browndyestuff.

11. The method of making a dye from bituminous coals which comprisesmixing time part'by weight of coal with up to about eight parts byweight of nitric acid added in small amounts, heating the mixture at atemperature below the decomposition temperature of said acid afterinitial exothermic reaction has abated to complete the reaction, washingthe treated coal to remove residual acid, extracting the washed coalwith an organic acidic material to recover solution of dye stuff, thenextracting a further amount of dyestuff with an aqueoussolution ofalkali.

HERBERT B. CHARMBURY.

